#include<bits/stdc++.h>
using namespace std;
int n,board[100001][2],dp[100001][2]; //1based, [idx][0,1]
int main(){
int tc;
scanf("%d",&tc);
while(tc--){
scanf("%d",&n);
for(int j=0; j<2; j++){
for(int i=1; i<=n; i++){
scanf("%d",&board[i][j]);
}
}
memset(dp,0x00,sizeof(dp));
dp[1][0]=board[1][0],dp[1][1]=board[1][1];
dp[2][0]=board[1][1]+board[2][0],dp[2][1]=board[1][0]+dp[2][1];
int ret=0;
for(int i=3; i<=n; i++){
for(int j=0; j<2; j++){
dp[i][j]=max(dp[i-1][!j],dp[i-2][!j])+board[i][j];
ret=max(ret,dp[i][j]);
}
}
printf("%d\n",ret);
}
}
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